A Sampling Procedure to Determine the Nitrogen Content in Opuntia ficus-indica Cladodes
Keywords:Opuntia ficus-indica; nitrogen content; cladode N-distribution; representative sample.
The objective of this study was to determine which part of the nonfruiting cladodes of Opuntia ficus-indica f. inermis (Web.) Le Houér. would represent the average nitrogen content of the entire cladode for taking minimally destructive samples. Core samples (2.1-cm diameter) were taken from 91 sites of 1-year old cladodes. Three replicates of 6 cladodes for the whole-cladode mean and 3 replicates of 6 cladodes for the core samples were used. The cladodes or cores (from each location) were bulked for each replicate. Nitrogen was analyzed by the Kjeldahl method. Data were statistically analyzed using the T-test for independent samples. It was found that 40 site-sampling locations that are grouped in a rectangular fashion in the central-basal zone of the cladodes faithfully represent the average N-concentration of the entire cladode (mean ±95% CI = 8.12 ±0.60 mg g-1 DW).